1. Field of the Invention
The present invention relates to stable and non-corrosive polysulphides derived from at least two olefins, suitable as additives for lubricating and industrial oils and to their process of manufacture.
According to a particular embodiment of this process, the invention relates also to the products obtained from isobutylene and diisobutylene used as starting olefins.
2. Description of the Prior Art
The presently known olefin polysulphides suitable as additives for oils have a particular sulphur content according to the nature of the starting materials. This sulphur content is not variable at will and numerous known processes do not permit a whole range of polysulphides to be available having, for example, a proportion of sulphur of 22 to 45%.
All these processes apply the two following principal reactions, namely: (1) reaction of a sulphur chloride with the starting olefin compound and (2) treatment of the resulting product with an alkali metal sulphide.
The reaction conditions vary from one process to the next. The starting olefin compound may be constituted by a single olefin, by a mixture of olefins, or of olefins and hydrocarbons. Such processes are, for example, described in U.S. Pat. Nos. 2,249,312; 3,471,404; 3,068,218; 3,697,499; 3,703,505; 3,703,504. The products resulting from the process described in U.S. Pat. No. 2,249,312 have generally a non-negligible proportion of chlorine, the proportion of sulphur depending to a high degree on the nature of the one or more starting olefins. U.S. Pat. No. 3,471,404 describes a process consisting of reacting sulphur monochloride with the olefin compound and treating the product resulting from this reaction with an alkali metal sulphide and free sulphur, then reacting the resulting product with an aqueous solution of a mineral base to lower the final proportion of chlorine. Although the exact structure of the final product is not known, it is specified in the patent that this product may consist of monomers containing sulphur or of monomers coupled together by a sulphur bridge to form a cyclic structure; it is thought that about 75% of the product, or more, consists of monomeric sulphur and of their cyclic derivatives.
The process described in U.S. Pat. No. 3,068,218 consists of reacting sulphur chloride with an olefin hydrocarbon in the presence of a mixture of water and an oxygen-containing organic compound miscible with water of the type of alcohol, acetone, or aldehyde. The chlorine content of the final product is far from being negligible and may be prejudicial to the result expected in the application of this product as an additive to lubricating oils.
As for U.S. Pat. No. 3,697,499, this patent describes a process in which sulphur monochloride is reacted with an olefin compound, treating the resulting product by means of an alkali metal sulphide in the presence of free sulphur in a solvent medium comprising an alcohol and water, then reacting the product resulting therefrom with a mineral base. The final product, although the exact structure is unidentified, includes, it is thought, cyclic units.
U.S. Pat. No. 3,703,505 describes a process consisting of subjecting an olefin hydrocarbon to sulphohalogenation by means of sulphur chloride to form a sulphochlorinated organic intermediate, then proceding with sulphuration and dehalogenation on the intermediate product by reaction with an alkali metal sulphide, the process being applied with the addition of a base enabling the formation of a colored product to be avoided, this base being of the amide, hydroxide, carbonate, bicarbonate or acetate of alkali metal type. The chlorine content of the one or more products obtained according to this process remains all the same of the order of 0.2 to 0.5%.
Finally, U.S. Pat. No. 3,703,504 describes a process consisting of reacting the olefin hydrocarbon with sulphur monochloride in the presence of an alcohol to form a sulphochlorinated intermediate product which is then reacted, in the presence of a relatively large amount of isopropanol, with an aqueous solution of sodium monosulphide derived from spent petroleum refinery liquors. The sulphur content of the products resulting from this process is high for a relatively low chlorine content (of the order of 0.1%).
All these processes may be applied to a single type of olefin or to mixtures of olefins. They do not however permit the sulphur content to be varied at will.
It is an object of the present invention to enable the proportion of sulphur to be varied and, in the particular case of its application to isobutylene and to diisobutylene taken as starting olefins, to provide a whole range of polysulphide products having a proportion of sulphur of 22 to 45% for a proportion of chlorine in the vicinity of zero, i.e. substantially zero.